Hi Joyce. I've been to Germany twice - 2011 and just returned a week ago. I am in my mid-50's. Both have been lovely experiences; however, I would say I am certainly NOT an expert on the area.
From my personal experience with your current choices:
- Rothenburg ob der Tauber is a beautiful little town.
- Nuremberg offers so many things to see, but I especially liked the
Old Town.
- Dachau is a somber experience but so worthwhile.
- I am assuming you will see Neuschwanstein (and Hohenschwangau) while
in Fussen, but if not, I do recommend those.
- I've not been to Salzburg.
- Cochem is such a lovely little town right on the Moselle River. The
castle there and Burg Eltz are beautiful.
For our 2011 trip, we traveled mostly in the Bavaria state, and also visited Innsbruck (beautiful town!) and Vienna in Austria. I can also recommend Oberammergau, Germany to visit. Many of the houses there are beautifully (fresco) painted, as well as being constructed with the lovely half-timbers.
For the 2014 trip, we traveled to small towns and visited Christkindl Markets and a few historical sites. Some of the loveliest small towns on this trip were Cochem, Bernkastel-Kues, Erfurt, Altotting, and Gengenbach.
I have never driven in Germany so I cannot really speak to the good/bad of doing so. I know the countryside is very beautiful. However, I would recommend train travel. You get to see some of the beauty of the country from the train but you travel in far less time than by car. And as someone else has already mentioned, parking is not always easy in many places. Perhaps you could divide your trip and drive one of the most picturesque parts you plan to travel to when you have plenty of time. I don't know if that is advisable but if you can determine a "central" place to stay, perhaps Nuremberg, and then choose one destination to drive to, you could have the best of both worlds. I have found the train system to be quite efficient and easy.
Enjoy your trip to Germany! I would love to return there some day!